Conventionally, there has been proposed a driving device for driving a driven body with use of an electromechanical transducer (piezoelectric element). Such a driving device is used for driving a lens in an optical device, e.g., for driving an imaging lens on a camera.
Conventionally, such a technical field includes Conventional Examples A and B below.
Conventional Example A is an invention that relates to a driving device including: a piezoelectric element capable of expanding and contracting in driving directions (i.e., directions along an optical axis) in which a body tube is driven; and a driving member joined to an end of the piezoelectric element. Conventional Example A is disclosed, for example, in Patent Literature 1 or Patent Literature 2. In Conventional Example A, the driving member is in engagement with the body tube. Moreover, the expansion and contraction of the piezoelectric element in the directions along the optical axis causes frictional force between the driving member and the body tube, and the frictional force causes the body tube to be driven in the directions along the optical axis.
FIG. 37 is an explanatory diagram for explaining the configuration of the driving device of Conventional Example A. As shown in FIG. 37, the driving device of Conventional Example A includes a piezoelectric element 301, a driving member 302 in the shape of a rod, a body tube (driven body) 304, a lens 3011, an imaging element 301 such as a CCD, and a circuit substrate 3013, all of which are housed in a housing 306.
The driving member 302 has an end joined to the piezoelectric element 301. Moreover, the body tube (driven body) 304 is in frictional engagement with the driving member 302.
Further, the body tube 304 has the lens 3011 fitted therein, and has the imaging element 3012 disposed therebelow. The circuit substrate 3013 has the imaging element 3012 fixed thereto by soldering or the like.
In the driving device of FIG. 37, the piezoelectric element 301 expands and contracts in the directions of the arrow; therefore, the driving member is driven in the directions along the optical axis. Accordingly, the body tube 304, which is in frictional engagement with the driving member 302, is driven in the directions along the optical axis.
Further, Conventional Example B is an invention that relates to an actuator having a plurality of piezoelectric elements joined to a mirror. Conventional Example B is disclosed, for example, in Patent Literature 3. Conventional Example B electrically controls bending of the plurality of piezoelectric elements, thereby tilting the mirror in a desired direction.
Further, a driving device using a piezoelectric element is disclosed, for example, in Patent Literature 4 or Patent Literature 5, as well as Patent Literatures 1 to 3 above.
The invention disclosed in Patent Literatures 4 and 5 is an invention that relates to a driving device including a piezoelectric element capable of expanding and contracting in driving directions (i.e., directions along an optical axis) in which a body tube is driven; and a driving member joined to an end of the piezoelectric element. Moreover, in Patent Literatures 4 and 5, the expansion and contraction of the piezoelectric element in the directions along the optical axis causes frictional force between the driving member and the body tube, and the frictional force causes the body tube to be driven in the directions along the optical axis. Further, Patent Literature 5 describes a driving device including a preload spring for imparting a preload to the body tube in a direction perpendicular to the direction of expansion of the piezoelectric element.
However, Conventional Examples A and B have the following problems.
That is, in the driving device of Conventional Example A, the piezoelectric element 301 is joined to an end of the driving member 302 along the optical axis, and the directions of expansion and contraction of the piezoelectric element 301 and the driving directions of the body tube 304 coincide with each other. This causes the driving member 302 and the piezoelectric element 301 to be arranged in a line along the driving directions (i.e., to be stacked), thus making it difficult to achieve a reduction in height of the driving device.
Further, in Conventional Example B, the amount of driving of the mirror is limited by the amount of displacement of the piezoelectric element.
Patent Literature 1: Japanese Patent Application Publication, Tokukaihei, No. 4-69070 A (Publication Date: Mar. 4, 1992)
Patent Literature 2: Japanese Patent Application Publication, Tokukaihei, No. 7-298656 A (Publication Date: Nov. 10, 1995)
Patent Literature 3: Japanese Patent Application Publication, Tokukai, No. 2003-209981 A (Publication Date: Jul. 25, 2003)
Patent Literature 4: Japanese Patent Application
Publication, Tokukai, No. 2007-74890 A (Publication Date: Mar. 23, 2007)
Patent Literature 5: Japanese Patent No. 3171022 (Registration Date: Mar. 23, 2001)